Add override keyword in various places

As were pointed out by GCCs -Wsuggest-override

Author: pbauman

include/base/libmesh_exceptions.h

@@ -124,7 +124,7 @@ class SolverException: public std::exception
   /**
    * Override the what() function to provide a generic error message.
    */
-  virtual const char * what() const noexcept
+  virtual const char * what() const noexcept override
   {
     // std::string::c_str() is noexcept in C++11, so it's safe to call
     // in what() because it can't throw.

include/error_estimation/adjoint_refinement_estimator.h

@@ -97,7 +97,7 @@ class AdjointRefinementEstimator : public ErrorEstimator
   virtual void estimate_error (const System & system,
                                ErrorVector & error_per_cell,
                                const NumericVector<Number> * solution_vector = nullptr,
-                               bool estimate_parent_error = false);
+                               bool estimate_parent_error = false) override;
 
   /**
    * This is an accessor function to access the computed global
@@ -108,7 +108,7 @@ class AdjointRefinementEstimator : public ErrorEstimator
     return computed_global_QoI_errors[qoi_index];
   }
 
-  virtual ErrorEstimatorType type() const;
+  virtual ErrorEstimatorType type() const override;
 
   /**
    * How many h refinements to perform to get the fine grid

include/numerics/const_fem_function.h

@@ -56,18 +56,18 @@ class ConstFEMFunction : public FEMFunctionBase<Output>
   ConstFEMFunction & operator= (ConstFEMFunction &&) = default;
   virtual ~ConstFEMFunction () = default;
 
-  virtual std::unique_ptr<FEMFunctionBase<Output>> clone () const
+  virtual std::unique_ptr<FEMFunctionBase<Output>> clone () const override
   {return libmesh_make_unique<ConstFEMFunction>(*this); }
 
   virtual Output operator() (const FEMContext &,
                              const Point &,
-                             const Real /* time */ = 0.)
+                             const Real /* time */ = 0.) override
   { return _c; }
 
   virtual void operator() (const FEMContext &,
                            const Point &,
                            const Real,
-                           DenseVector<Output> & output)
+                           DenseVector<Output> & output) override
   {
     for (auto i : index_range(output))
       output(i) = _c;

include/numerics/parsed_fem_function_parameter.h

@@ -72,22 +72,22 @@ class ParsedFEMFunctionParameter : public ParameterAccessor<T>
   /**
    * Setter: change the value of the parameter we access.
    */
-  virtual void set (const T & new_value) {
+  virtual void set (const T & new_value) override {
     _func.set_inline_value(_name, new_value);
   }
 
   /**
    * \returns A constant reference to the value of the parameter we access.
    */
-  virtual const T & get () const {
+  virtual const T & get () const override {
     _current_val = _func.get_inline_value(_name);
     return _current_val;
   }
 
   /**
    * \returns A new copy of the accessor.
    */
-  virtual std::unique_ptr<ParameterAccessor<T>> clone() const {
+  virtual std::unique_ptr<ParameterAccessor<T>> clone() const override {
     return libmesh_make_unique<ParsedFEMFunctionParameter<T>>(_func, _name);
   }
 

include/numerics/parsed_function_parameter.h

@@ -70,22 +70,22 @@ class ParsedFunctionParameter : public ParameterAccessor<T>
   /**
    * Setter: change the value of the parameter we access.
    */
-  virtual void set (const T & new_value) {
+  virtual void set (const T & new_value) override {
     _func.set_inline_value(_name, new_value);
   }
 
   /**
    * Getter: get the value of the parameter we access.
    */
-  virtual const T & get () const {
+  virtual const T & get () const override {
     _current_val = _func.get_inline_value(_name);
     return _current_val;
   }
 
   /**
    * \returns A new copy of the accessor.
    */
-  virtual std::unique_ptr<ParameterAccessor<T>> clone() const {
+  virtual std::unique_ptr<ParameterAccessor<T>> clone() const override {
     return libmesh_make_unique<ParsedFunctionParameter<T>>(_func, _name);
   }
 

include/utils/parameters.h

@@ -215,18 +215,18 @@ class Parameters
     /**
      * String identifying the type of parameter stored.
      */
-    virtual std::string type () const;
+    virtual std::string type () const override;
 #endif // LIBMESH_HAVE_RTTI
 
     /**
      * Prints the parameter value to the specified stream.
      */
-    virtual void print(std::ostream &) const;
+    virtual void print(std::ostream &) const override;
 
     /**
      * Clone this value.  Useful in copy-construction.
      */
-    virtual Value * clone () const;
+    virtual Value * clone () const override;
 
   private:
     /**